Electric transmission



March 27, 1934. MCCORMICK 1,952,450

ELECTRIC TRANSMISSION Filed NOV. 5, 1931 Fig.1

TO CRANK SHA Inventor N CORMICK Patented Mar. 2 7, 1934 v UNITED STATES PATENT OFFICE ELECTRIC TRANSMISSION Bradley McCormick, St. Louis, Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware Application November 5, 1931, Serial No. 573,042

8 Claims. (01. 172-239) My invention relates to variable ratio transbooster dynamo is directly connected with brush mission apparatus for vehicles and more particu- 13 of the clutch dynamo by wire 19, thereby closlarly to the electro-magnetic type of transmission ing the electrical circuit between the booster dyin which two dynamo-electric machines are inname and the clutch dynamo.

terposed between the driving shaft and the driven The brushes l6 and 18 of the booster dynamo on shaft. are mounted upon a ring 20 provided with ex- The principal object of my invention is to proternal gear teeth. The ring 20 is geared to the vide electrical transmission of the type referred shaft 21 of the armature 22 of a brush shifting to, with control means which positively causes motor by means of an idler gear 23 and a pinion both of the dynamo-electric machines to act as 24 fixed to shaft 21. The ring is provided with generators to produce a braking action upon the a radial extension 25 which is adapted to engage vehicle regardless of the speed of the driving the fixed stop 26. A spiral spring 27 is secured shaft and the functions of the dynamo-electric at one of its ends to the motor shaft 21 and at machines at the time the control means is operits other end to a fixed part of the vehicle. This 1 ated. spiral spring is adapted to bias the extension 25 Other objects will become apparent from the to such a position relative to the stop 26 that following description of my invention taken in the brushes l6 and 18 will be 180 electrical deconnection with the accompanying drawing in grees from the position they will occupy when which Figure 1 is a diagrammatic representathe extension 25 is in engagement with the stop 0 tion of an electrical transmission embodying my 26. invention; and Figure 2 is a diagrammatic illus- A third brush generator provided with an tration of the means employed for shifting the armature 28, is connected to the crank shaft 1 brushes of one of the dynamo-electric machines. of the internal combustion engine. The armature Referring to the drawing in detail, 1 is the is provided with two main brushes 29 and 30 5 crank shaft of an internal combustion engine which are connected to a battery 31. The field upon which is mounted the flywheel 2 in the 32 of the generator is connected across the main usual manner. The armature 3 of a dynamobrush 30 and the third brush 33. This third electric machine, hereinafter called the booster brush generator is identical to the well known dynamo, is connected at one end to the crank third brush lighting generator used on present 30 shaft 1 and has secured to its other end a bevel day motor vehicles and is adapted to produce gear 4. The driven shaft 5, connected to the increased voltage across the brushes 29 and 33 wheels of the vehicle, is in alignment with the upon increased speed of the armature. The armature 3 and has secured on its inner end a voltage across the brushes 29 and 30 remains pair of radially extending short shafts 6 which approximately constant regardless of the speed 35 areinclined at an angle to the axis of the driven of the generator. shaft. A pair of bevel gears 'l are rotatably The brush 34 of the brush shifting motor is mounted on the short shafts 6 and engage the directly connected by wire 35 to the battery 31 bevel gear 4. A hollow shaft 8 is rotatably and to the brush 29 of the third brush generator mounted upon the driven shaft and has secured through the usual reverse current relay 54.

40 thereon a bevel gear 9 in engagement with the Brush 36 of the brush shifting motor is connected bevel gears 7. The armature 10 of a second by means of wire 37 to the brush 33 of the gendynamo-electric machine, hereinafter referred to erator. It is, therefore, seen that there will be as the clutch dynamo, is also secured to the an increased flow of current through the armahollow shaft 8 and is provided at one end with a ture of the brush shifting motor upon increased 45 commutator 11 cooperating with fixed brushes speed of the generator armature 28 since the 12 and 13. voltage across brushes 29 and 33 increases with The booster dynamo and the clutch dynamo the increase of speed of the armature 28. The are electrically connected in series. This series field 38 of the brush shifting motor is connected relation is secured by connecting brush 12 to the across the main brushes 29 and 30 of the third 50 fixed field winding 14 ofthe clutch dynamowhich brush generator by connecting one end of the in turn is connected to the fixed field winding field by conductor 39 to conductor 35, and the 15 of the booster dynamo, the latter field windother end to a ground 40 through wire 41. The ing being electrically connected to the brush 16 brush 30 of the third brush generator is grounded cooperating with the commutator 17 of the at 42 to complete the circuit. It is thus seen 55 booster dynamo. The second brush 18 of the that since the voltage across the brushes 29 and 30 is practically constant, the voltage across the terminals of field 38 of the brush shifting motor will also be practically constant.

The operation of the apparatus just described is as follows: Assuming the car is standing still and the internal combustion engine has been started, the driven shaft 5 will be stationary since the entire load of the vehicle is connected thereto. The crank shaft 1 will, therefore, rotate the armature 3 of the booster dynamo and by means of the gears 4, 7 and 9 the armature 10 of the clutch dynamo will be rotated in the opposite direction at a greater speed due to the fact that gear 9 is smallerthan gear 4. The direction of rotation of the armature 10 will cause the clutch dynamo to operate as a generator and the direction of rotation of the armature 3 will cause the booster dynamo to operate as a motor due to the fact that the brushes thereof are held in a motor position by the spiral spring 2'7. The armature 10 of the clutch dynamo will send current through the field 15 and the armature 3 of the booster dynamo to cause the booster dynamo to add to the torque of the crank shaft and increase the torque on the driven shaft by means of gears 4, '7 and 9 since the current generated by the clutch dynamo produces a torque opposing rotation of the armature and the gear 9 connected thereto. This action continues until the torque on the driven shaft is sufllcient to start the vehicle. The faster the driven shaft rotates, due to decrease in load thereon, the slower will be the rotation of the clutch dynamo armature and of the gear 9 as a result of the opposing torque produced by the generated current. A point will be reached, when the load has decreased sufflciently, where the clutch dynamo armature will be held substantially stationary by the torque opposing the rotation of the clutch dynamo armature. The ratio of speed between the crank shaft and the driven shaft is then dependent upon the ratios of the gears 4, 'l and 9, gear 9 being stationary. The speed of the crank shaft at this time has increased to such a value that the voltage across the brushes 29 and 33 of the third brush generator and, therefore, the voltage across the brushes 34 and 36 of the brush shifting motor, is large enough to cause the armature 22 of the brush shifting motor to have sufficient torque to wind up the spiral spring 27 to shift the ring 20 and move extension 25 against stop 26 and thereby shift the brushes 16 and 18 of the booster dynamo through 180 electrical degrees to change the booster dynamo from a motor to a generator. The changing of the booster dynamo from a motor to a generator causes current to be supplied to the clutch dynamo, causing it to operate as a motor whose armature rotates in the same direction as the armature 3 of the booster dynamo.

My invention comprises means wherebythe booster dynamo and clutch dynamo can both be caused to act as generators under any conditions of operation and thereby produce a braking action on the driven shaft 5 of the vehicle. By means of switch 46 the brushes 12 and 13 of the clutch dynamo 10 may be connected together through a suitable resistance 43. The switch 46 is secured to a foot controlled switch operating member 47 which is also provided with a switch member 48 connected to the wire 3'! leading from the brush 36 of the brush shifting motor. The switch 48 may be engaged with contacts 49 or 50, the former of which'is connected to the brush 33 of the third brush generator, and the latter of which is connected to a ground 51. A spring 52 normally biases the switch 48 against the contact 49 and the switch 46 to open position.

Assuming that the vehicle is moving at'a normal rate of speed with the booster dynamo operating as a generator and the clutch dynamo as a motor and it is desired to stop or retard the vehicle, the operator will shut off" the engine and press the switch controlling member 47, thereby placing the resistance 43 in circuit with the armature 10 of the clutch dynamo. The movement of the switch controlling member will also simultaneously connect the armature of the brush shifting motor across the storage battery 31 and bring switch 48 into engagement with contact 50. The decrease in engine speed and, therefore, the decrease in voltage across the brushes 29 and 33 of the third brush generator will have no eilect upon the torque of the brush shifting motor as it will now be receiving a constant voltage from the battery 31 which will be sufficient to maintain the booster dynamo brushes in generator position. As the booster dynamo continues to act as a generator, it will supply current to excite field 14 of the clutch dynamo. Since the armature 3 of the booster dynamo has slowed down, the action of the gears 4, 'I and 9 will cause the clutch dynamo to rotate at a faster rate of speed in the same direction of rotation as the driving and driven shafts. An E. M. P. will now be set up in the clutch dynamo armature due to the excitation of field 14. This will oppose the E. M. F. of the booster dynamo and will also cause a current to flow through the resistance 43. When the current in the resistance circuit becomes greater than the exciting current from the booster dynamo, the clutch dynamo will act as a gen- 115 erator. It is thus seen that by means of my invention both dynamo electric machines positively act as generators when the switch operating mem ber 4'1 is operated, regardless of the speed of the engine or the functions being performed by the dynamo electric machines at the time a braking action is desired.

The brushes 16 and 18 may also be held in generator position by a mechanical means between the foot-operated member 47 and the ring 2, which is operative only when the member 4'1 is depressed.

Although I have described a specific type of electrical transmission to which I have applied my invention, it is obvious that it may be applied to other types of electrical transmission to secure the same results and I, therefore, do not intend that the scope of my invention be limited except as defined in the appended claims.

Having fully described my invention, what I 5 claim as new and desire to secure by Letters Patent of the United States is:

1. In apparatus of the class described, the combination of a driving shaft, a driven shaft, an electrical transmission for transmitting power from the driving shaft to the driven shaft, said transmission comprising a pair of electrically and mechanically connected dynamo-electric machines one of which is provided with shiftable brushes, means responsive to the speed of one of the shafts for shifting said brushes to cause said dynamo-electric machine to act as a generator, and means for causing both of said dynamo-electric machines to simultaneously act as generators regardless of the speed of the shaft to which the brush shifting means is responsive.

2. In apparatus of the class described, the combination of a driving shaft, a driven shaft, means for transmitting power from the driving shaft to the driven shaft comprising a pair of dynamoelectric machines, one of which is provided with shiftable brushes whereby it may be caused to act either as a motor or as a generator, means biasing said brushes to motor position, means responsive to the speed of one of the shafts for maintaining said brushes in generating position, and independently operable auxiliary means for maintaining the brushes in said last named position.

3. In apparatus of the class described, the combination of a driving shaft, a driven shaft, an electrical transmission for transmitting power from the driving shaft to the driven shaft, said transmission comprising a pair of electrically and mechanically connected dynamo-electric machines one of which is provided with shiftable brushes, means responsive to the speed of one of the shafts for shifting said brushes to cause said dynamo-electric machine to act as a generator, a braking circuit comprising a resistance and a switch in circuit with the armature of the other dynamo-electric machine, and means operable with the switch for so controlling the shiftable brushes that said first mentioned dynamo-electric machine will act only as a generator when said switch is closed.

4. In apparatus of the class described, the combination of a driving shaft, a driven shaft, an electrical transmission for transmitting power from the driving shaft to the driven shaft, said transmission comprising a pair of electrically and mechanically connected dynamo-electric machines one of which is provided with shiftable brushes whereby the dynamo-electric machine may be caused to act as a motor or as a generator, means biasing said brushes to motor position, a motor for shifting the brushes to generator position, and means for causing said motor to hold said brushes in generator position and for simultaneously causing the other dynamo-electric machine to act as a generator.

5. In apparatus of the class described, the combination of a driving shaft, a driven shaft, an electrical transmission for transmitting power from the driving shaft to the driven shaft, said transmission comprising a pair of electrically and mechanically connected dynamo-electric machines one of which is provided with shiftable brushes whereby said machine may be caused to act as a motor or as a generator, means biasing said brushes to motor position, an auxiliary motor for shifting the brushes, means responsive to the speed of one of said shafts for impressing a variable voltage on the motor, and independently operable means for impressing a voltage on said motor independent of the speed of said shaft to cause the motor to maintain said brushes in generator position.

6. In apparatus of the class described, the combination of a driving shaft, a driven shaft, an electrical transmission for transmitting power from the driving shaft to the driven shaft, said transmission comprising a pair of electrically and mechanically connected dynamo-electric machines one of which is provided with shiftable brushes whereby the dynamo-electric machine may be caused to act as a motor or as a generator, means biasing said brushes to motor position, a motor for shifting the brushes, a generator responsive to the speed of one of the shafts for sup plying a variable voltage to said motor whereby the auxiliary motor will shift the brushes to generator position upon a given speed of the shaft being attained, a resistance and a switch in circuit with the armature of the other dynamoelectric machine, and means operable when the switch is in closed position for impressing a voltage on said auxiliary motor to cause it to maintain said brushes in generator position.

7. In apparatus of the class described, the combination of a driving shaft, a driven shaft, a pair of electrically and mechanically connected dynamo-electric machines for transmitting power from the driving shaft to the driven shaft, one of said dynamo-electric machines being provided with shiftable brushes to cause said machine to act either as a motor or as a generator, the other of said dynamo-electric machines acting as a generator to supply power to the first named machine when the brushes are in motor position and as a motor when the first named machine acts as a generator, and means comprising a single operable member for positively causing both of said dynamo-electric machines to act as generators.

8. In apparatus of the class described, the combination of a driving shaft, a driven shaft, a pair of electrically and mechanically connected dynamo-electric machines for transmitting power from the driving shaft to the driven shaft, means responsive to the speed of one of the shafts for causing one of the dynamo-electric machines to act either as a motor or as a generator, the other of said dynamo-electric machines acting as a generator to supply power to the first named machine when it is acting as a motor and as a motor when the first named machine acts as a generator, and means comprising a single operable member for positively causing both of said dynamo electric machines to act as generators.

BRADLEY MCCORMICK. 

